1. Field of the Invention
The present invention relates to an apparatus for attenuating image noise, and more particularly, to a method of attenuating noise contained in an image signal according to the extent of the movement of a signal. The present application is based on Korean Application No. 2001-62670, filed Oct. 11, 2001, which is incorporated herein by reference.
2. Description of the Related Art
Advancements in the quality and variety of image appliances is causing demand for high-definition image appliances. In response to this demand, apparatuses for removing noise contained in image signals have been developed. In general, low-pass filters or recursive filters are used to filter out noise in a transmitted image signal.
FIG. 1 is a block diagram of an embodiment of a recursive filter according to a conventional apparatus for attenuating image noise. Referring to FIG. 1, an image signal containing noise and an image signal that is delayed for one frame by a delayer 140 are combined in a subtracter 110 to generate an offset signal. In this structure, the offset signal is limited to a lower level by a limiter 120. At this time, the lower the level of the offset signal is limited by the limiter 120, the more the noise can be reduced. However, this increases an artifact according to scene motion. Finally, an output of the offset signal, which is attenuated by the limiter 120, is combined with an image signal input by an adder 130. As a result, the noise contained in the image signal is canceled by the adder 130. Then, the image signal whose noise was attenuated is fed back to the delayer 140 to be used in the next frame.
As described above, a recursive filter is designed to operate on the basis of the correlation between frames separated at two-frame intervals. Thus, noise-reducers such as a recursive filter tend to have inadequate effects since the correlation between frames separated at two-frame intervals is relatively low.